make sillyrename (try to) use LINK operation rather than RENAME.
PR/33861 from Jed Davis. he provided the almost same patch.
according to him, it also happen to be what opensolaris does in this case.
from the PR:
> In nfs_rename(), if the destination appears to exist and is "in use"
> (this check is apparently satisfied even if the file isn't in use by
> anything except the rename itself), it will sillyrename it, then delete
> the sillyrenamed file even if the rename fails -- for instance, because
> the "from" file no longer exists on the server.
> mkdir a b; touch a/x; perl -e 'fork(); rename("a/x","b/x") or die "$!\n"'
>
> Afterwards, neither a/x nor b/x will exist.
> 1) Lookup of b/x; fails with NOENT.
> 2) Rename from a/x to b/x; succeeds.
> 3) Lookup of b/x; fails with NOENT.
> 4) Rename from b/x to b/.nfsA23a3; succeeds.
> 5) Rename from a/x to b/x; fails with NOENT.
> 6) Remove of b/.nfsA23a3; succeeds.
- struct timeval time is gone
time.tv_sec -> time_second
- struct timeval mono_time is gone
mono_time.tv_sec -> time_uptime
- access to time via
{get,}{micro,nano,bin}time()
get* versions are fast but less precise
- support NTP nanokernel implementation (NTP API 4)
- further reading:
Timecounter Paper: http://phk.freebsd.dk/pubs/timecounter.pdf
NTP Nanokernel: http://www.eecis.udel.edu/~mills/ntp/html/kern.html
My understanding is that the CLRSIG() is supposed to clear the signal
that was sent to the syncer process to prevent it from being delivered
to the syncer process in case unmounting fails, so that the syncer process
does not die while the filesystem is still mounted. The typical scenario
is, the syncher process is tsleep()ing in the kernel, and waking up when
it needs to do work. If someone sends a signal to it, eg. kill -TERM
the mfs process, then the kernel will try to unmount the mfs filesystem
before delivering the signal to the process. If that unmount fails, then
we should not really kill the process because that will hang the mount.
So we call CLRSIG() to stop the signal from being delivered.
So the first call to issignal() will return the signal number that was
sent to the syncer process (unless someone malicious was able to send
a lower numbered signal between the time tsleep() returned and we called
issignal()... something that is not really easy to do). But you are
right, we should not be calling it many times as a side effect of this
macro.
Rewrite CLRSIG() clear all the signals and call issignal() the correct
number of times.
- remove GOP_SIZE_READ/GOP_SIZE_WRITE flags.
they have not been used since the change.
- ufs_balloc_range: remove code which has been no-op since the change.
thanks Konrad Schroder for explaining the original intention of the code.
- ffs_gop_size: don't extend past eof, in the case of GOP_SIZE_MEM.
otherwise genfs_getpages end up to allocate pages past eof unnecessarily.
- use vmspace rather than proc or lwp where appropriate.
the latter is more natural to specify an address space.
(and less likely to be abused for random purposes.)
- fix a swdmover race.
